1. Field of the Invention
The present invention relates generally to an engine mount and more specifically to an engine mount which is filled with a electrorheopectic fluid.
2. Description of the Prior Art
JP-A-57-84220 discloses an ERF-filled engine mount which includes a main working chamber defined in part by an elastomeric member, an orifice arrangement which provides fluid communication between the main working chamber and an auxiliary chamber, and a movable element which is disposed in a gutter defining casing.
In this arrangement, when vibrations in relatively low frequency ranges such as those in which engine idling and engine shake occur, the movement of the slug of fluid which is contained in the orifice passage is induced in a manner which attenuates the amount of vibrational energy which is transmitted to the chassis from the power unit.
When vibration which falls in a relatively high vibrational range such as that which tends to induce reverberation noise in the vehicle cabin, is applied to the mount, the movable element is excited to undergo displacement in a manner wherein the gutter arrangement functions to attenuate the vibration and thus reduce the amount of cabin noise.
In order to derive the appropriate vibration transmission attenuation in the lower vibration ranges it necessary to ensure that the movable element does not move. In other words, when high frequency low amplitude vibration is applied, the amount of movement of the movable element should be limited to small value while when relatively large amplitude low frequency vibration is applied, the movement should be prevented.
However, this prior proposed arrangement suffers from the drawback that when the vibration applied exhibits a relatively low frequency and a relatively low amplitude, such as tends to occur during engine idling, the pressure which is developed in the main working chamber tends to escape via the gutter and reduces the required amount of fluid movement in the orifice passage.
Further, when large amplitude engine shake type vibrations are produced the pressure changes in the main working chamber are reduced by the amount which the fraction of fluid which is contained in the gutter arrangement moves and the full effect of the orifice passage or passages cannot be realized.